Therefore, in the present study the expression of LRP5, LRP6 or β-catenin was inactivated in the midbrain DA neurons of the LRP6, LRP6 or β-catenin CKO mice, and the alterations in the numbers of TH-ir neurons in the SNc and striatum of the MPTP-PD model were then investigated. Here, TH is linked to Parkinson disease.